This invention relates to optical processing, and more particularly to an optical correlator comprising a spatial light modulator optically coupled to a length of an optical guide.
Spatial light modulators (SLMs) have a diversity of applications in addition to their more commonly known application for display systems. One application is in optical correlation systems, which are processing systems designed to perform computationally intensive image correlation.
Conventionally, for optical correlator applications, the SLM is used to generate a reference image. A second image is captured from some sort of sensor input. The two images are then compared to determine the degree of correlation. The two dimensional imaging capabilities of the SLM make them especially useful for pattern recognition.
The determination of whether two images correlate can be made by means of either optical processing or with digital computer xe2x80x9cnumber crunchingxe2x80x9d. Many optical correlation systems are hybrid systems that use both optical and electrical components.
One aspect of the invention is an optical correlator that detects whether a given pattern of on and off illumination matches a portion of an optical bitstream. A spatial light modulator has at least one row of pixel generating elements. Each row generates a one-dimensional pattern of on or off illumination. An optical guide, such as an optical fiber, is optically linked to each row, such that a length of the optical guide receives the illumination from that row. The optical guide is further operable to transmit a bitstream of optical information. A detector is optically linked along the same length of the optical guide, such that the detector is operable to receive illumination representing the interaction of the bitstream and the illumination from the spatial light modulator.
An advantage of the invention is that the correlator may be used to continuously monitor for a particular bit pattern being transmitted down an optical guide, such as optical fiber used for telecommunications. The target pattern on the spatial light modulator may be easily and quickly changed. The interrogation of the bitstream occurs rapidly.
The analysis of the combined illumination in the light guide can range from simple optical processing to sophisticated digital algorithms. Fourier analysis of sum and difference, match and search, and filter and mix algorithms can be applied.